1. Field of the Invention
The present invention relates to an endoscopic system which provides a color picture by combining, for instance, the three primary color images, i.e., a red (R) image, a green (G) image, and a blue (B) image, and particularly to an improvement of a mechanism for adjusting the color and contrast of a color picture.
2. Description of the Prior Art
Endoscopic systems usually use a plane sequential method in which the color of an illuminating light is sequentially changed among R, G, and B colors, or a point sequential method in which an image is photographed with the three primary colors at the same time, or a simultaneous method.
In such prior art endoscopic systems, the color and contrast of a color picture are adjusted by stretching histograms of, for instance, R image, G image, and B image of the color picture. According to such a stretching adjustment, the contrast of the picture is enhanced but the color thereof which is an important factor in the color picture, tends to differ from the actual color.
As described in the above, according to the prior art, the histograms of the R, G, and B images are subjected to the stretching adjustment to enhance the contrast of the color picture, but it is difficult to always maintain the actual color of the picture.
Therefore, when the stomach of a patient is monitored by a prior art endoscopic system to see whether or not a cancer exists, it is frequently difficult to distinguish a delicate color difference between the cancer and a normal part. In addition, the prior art endoscopic systems are not provided with functions and mechanisms for executing a histogram equalization process of a hue image and a saturation image.